Process for the manufacture of hematite cast iron



' R.. P.ERRIN une 4,1940.

I PROCESS FOR THE MANUFACTURE OF HEMATITE CAST IRON Filed March 14, 1958Iv entom- Patented June 4, 1 940 sif Q. I I I 2,203,179

PROCESS FOR THE HEMATITE MANUFACTURE OF CAST IRON Ren Perrin, Paris,France, assignor to Societe dlllectr'ochimie, dElectromettalurgie et desAcieries Electriques dUginc, Paris, France, a

corporation of France Application March-14, 1938, Serial No. 195,842

' In France March 16, 1937 4 Claims.

lt has already been proposed to make hematite cast iron by means of theThomas converter starting from cast iron containing phosphorus by firsttransforming this cast iron into a dephos-' phorised steel and by thenrecarburising this steel by addition ofcarbon. The recarburation may beeffected either in the converter itself or by successive turning down ofthe converter with very short blowings or in a ladle by transfer.

in the same process it has been proposed to add to the metal during thereoarburation addi tions of materials producing evolution of heat inorder to increase the solubility of the carbon.

By the present invention I have discovered the means of effecting thisrecarburation in conditions such that:

l. The solution of the carbon is extremely rapid.

2. The addition of materials giving off heat to obtain an increase ofthe solubility of the carbon is in no way necessary.

3. The operation is very losses are very small.

4. The operation leads to high yields of the 5 recarburising materialand moreover yields which are extremely regular from one operation toanother.

5. The final composition of the cast iron obtained is extremely regularfrom one operation to another. a

In order to arrive at these results I propose to submit the material tobe recarburised-generally extra mild steel coming from the converter-andthe recarburising materialfor example coke or charcoal-to successiveenergetic intermixings 1 repeated at short intervals in an apparatusformed for example of two chambers arranged so as to permit with rapidfrequency the contents of one of the chambers to be poured into theother and reciprocally with a force suilicient to bring, during thepourings thus effected, thecarboniferous elements below the surface ofthe metal producing strong eddies. 1

Such an apparatus may be formed in particular simple and the heat of twochambers opposing mouth to mouth and l ment, the liquid steeland'the'carbon which it is desired to react are introduced into theapparatusand this is subjected to a series of successive oscillations orrotations which project the steel and carbon from one chamber into theother i reciprocally. The ratio between the volume of each chamber andthe charge of metal and solid reacting substance which is introducedtherein for treatment is so chosen that the height of fall of the saidcharge from one chamber into the other is sufiicient for thecarboniferous substance'to be entrained into the body of the metal andto produce strong eddies.

It is important however to explain how these successive pourings shouldbe effected for the success of the operation. If it is presumed that oneof the chambers of the apparatus contains liquid steel upon which forexample pieces of coke have been dropped and that the metal from thischamber is poured slowly into the other chamber, of the apparatus, thecoke having a density much u less than that of the metal will remain atthe, surface of the bath and only a very slow reaction and solution willbe produced.

If on the contrary the metal is poured with force, strong eddies will beproduced, the whole or a large part of the coke is entrained into thebody of the metal and experiment then shows that the'speed of thereactions and of the solution increases to a very considerable extent aswell as the regularity of the results obtained.

It is this phenomenon of entrainment of the coke into the body of themetal which is to be v sought, this entrainment is moreover alsofacilitated by the eddies which are produced by theshock of the moltenmetal against the walls.

It is important in all cases that the pouring. of the metal with thecarboniferoussubstance should be sufiiciently strong for there to bepenetration of the pieces of the carburising material into thebody ofthe metal which condition is the more diflicult to produce the'greaterthe difference between the density of this material and that of themetal. This result may be obtained in the most simple way for example inthe type of. apparatus described below. At each oscillamolten metal andthe recarburising material will give rise to considerable evolution ofcarbon I monoxide particularly at the beginning of the operation in thecase when one starts from an extra mild Thomas steel which is stronglyoxidised. In this case precautions should be taken so that the rapidityof the reaction is not such that it leads to an explosion or even toexpulsion of metal out of the apparatus.

Apart from the fact that the apparatus should be open to permit theoutlet of the gases as they are formed, two means may be employed toregulate the rapidity of the reaction.

1. The successive pourings may be slowed down. But in this case thepouring must remain sufficiently strong for there to be penetration ofthe carboniferous material into the body of the molten metal whichcondition is essential for rapid reaction.

2. The quantities of carboniferous material may be introducedperiodically by fractions in regulated proportions (at each pouring forexample) or even in a less divided form. It is important not to use toofine powder which may be partially taken away by the gases which areevolved.

The adjustment will be effected for each particular treatment byprevious tests.

It will be observed when operating under the conditions described abovethat in a very short time even when starting from an extra mild steel acast iron'having the desired carbon content will be obtained.

The starting materials to be utilised for recarburation may be coke,charcoal, anthracite or any other carboniferous material capable ofdissolving in the metal. They will be chosen as free from sulphur aspossible.

Although the addition of substances giving ofi heat is not necessary toeffect the dissolution of the carbon substances may if desired beintroduced' such as silicon or manganese or'other alloying elements withthe object of bringing th cast iron to the desired composition.

The process of the invention is capable of being applied in advantageousconditions in an apparatus such as that shown schematically by way ofexample in the accompanying drawing.

The apparatus comprises two chambers I and 2, relatively deep, connectedto one .another by their mouth and communicating with a -medial aperture3 open to the atmosphere. These two chambers areeonstituted by ametallic casing 4 provided with a refractory lining 5., The whole ismounted upon a, shaft 6 capable of turning in support bearings 'I. andreceives an alternating oscillatory movement by means of a drivingmechanism of suitable known typewhich is not shown. This, movementbrings turn by turn the.

chambers l and 2 into a position respectively high or low and with astrong inclination which causes Example of operation Into the apparatus3 metric tons of extra mild strongly oxidised steel were introduced.

phorus content 0.010%. 65 kgs. of coke with a low sulphur content wereadded.

The carbon content of this steel was 0.05%, the phos-'" To the apparatusa series of oscillations were imparted. An intense ebullitionoccurreddue to the action of the coke on ,the oxides present in themetal. The ebullition slowed down as the oscillations continued. Aftersix oscillations 65 kgs. of coke were added.

At the end of 12 oscillations in all the operation was terminated. Thecast iron obtained contained: C=3.5%; P=0.012%; S=0.025%.

The melting .point of the final metal being notably lower than that ofthe initial metal, 8.6-1

cording to the invention the heat which has become availableinconsequence of the difierences in temperature in question may beutilised to increase finally without expenditure of external heat orwithout necessarily having to develop internal heat, the weight of theinitial metal and.

Due to the fact that the metallic bath is at a temperature above itsmelting point and due likewise to the speed of the successive pourings,the

elements thus added dissolve rapidly in the bath even if they areintroduced cold, and this without the bath cooling below the temperaturewhich should be maintained for its subsequent use.

. There is obtained finally by recovery of the excess heat whichotherwise would be lost a weight of metal above that of the initialmetal increased by that of the solid reacting material which haspassedinto the: metal, for example if I the manufacture of cast ironiisconcernedwa weight of cast iron above that of the initial steelincreased by that of the carbon which has passed into the cast iron.

The proportionof the pieces or fragments of metal or of scrap or ofalloying elements which it is possibleto incorporate thus in the bathof. metal is considerable and may reach practically I 5% and evenmore ofthe initial weight ofcthe metal, but it is naturally limited: by thequantity of excess heat available in the cycle. It dependsalso onthestate of division in which are the.

materials to be melted, for example fine scrap metal or scrap iron orturnings will be'capable of dissolving very rapidly. This proportion mayreadily be determined in each case by-calcula- .tion or .even better byexperiment. -The importance of such metallic additions in the specialapparatus employed, resides .in the particularly economical utilisationwhich is thus made of these materials and of the excess heat, whichmaterialsare utilised normally by fusion in the electric. or Mar tinfurnace, that'isto say with expenditure of external heat.

What I claim is:

l. Theprocess of making .cast iron, which comprises subjecting moltenmild steel and solid re:

carburizing material simultaneously to a series of successive'rapidpouring's which are effected with a force suflicient to insure duringthese pourings an intimate and turbulent mixture of the metal andrecarburizing material, and during or at the end of the carburizingreaction adding solid metallic or alloying elements which are caused todissolve by means ofthe heat rendered available by reason of thedifference of the melting point of the initial metal and that of therecarburized metal.

oi' s'uccessive rapid pourings which are effected with a forcesufllcient to insure during these pourings an intimate and turbulentmixture of the metal. and recarburizing material, and dis- I solvingsolid metallic or alloying elements in the bath which has been at leastpartially carburized and without the supply of external heat to thebath.

3. The process of making cast iron, which comprlsessubjecting moltenmild steel and solid recarburizing material simultaneously to a seriesof successive rapid pouringswhich are eflected with a force sumcient toinsure during these pourin'gs an intimate and turbulent mixture of themetal t 3 ments in the bath which has been at least partially carburizedand without the supply of external heat to the bath.

4. v'I'he process 0! making cast iron, which comprises subiecting moltenmild steel and solid recarburizingmaterial simultaneously to a series ofsuccessive rapid pourings which are effected with a force sufllcient toinsure during these pourings an intimate'and turbulent mixture of themetal and recarburizing material, and continuing the pourings until thecarbon content of the bath is raised by an amount of the order of atleast 3.0%

and dissolving solid metallic or alloying elements in the bath which hasbeen at least partially carburized and without the supply of externalheat] to the bath, the mild steel being substantially free from sulphurand the carburizing reaction being carried out in the absence of addedoxidizing agents. v

RENE rmmm.

